The present invention relates to the field of the broadcasting of digital television programs and more particularly a method for generating and transferring at least one data stream in accordance with the DVB-T2 (Digital Video Broadcast) standard.
Historically, the ETSI (European Telecommunications Standards Institute) proposed a first standard, DVB-S, for broadcasting programs by satellite. This standard was divided into the standards DVB-C for cable network broadcasting and DVB-T for terrestrial broadcasting. These standards are referred to as first-generation DVB standards.
These standards share a common base. The programs are composed of multiplexed audio and video streams to which signaling information is added in the form of signaling tables known as SI/PSI (Service Information/Program Specific Information) tables. The resulting multiplexed stream is encapsulated in a transport layer in accordance with the MPEG-2 TS (Moving Picture Experts Group 2 Transport Stream) standard for broadcasting. These standards have certainly been successful and constitute a widespread television broadcasting technology.
At the present time, a new generation of these standards is being developed. In particular, terrestrial broadcasting is standardized in the form of a DVB-T2 standard. This new standard makes it possible to aggregate, in the same stream, several physical-layer tunnels referred to as PLPs (Physical Layer Pipes). Each of these physical layer tunnels consists of a multiplex of programs in a transport stream of the MPEG-2TS type having its own modulation parameters. These tunnels are connected together in a stream referred to as a T2-MI (Modulator Interface) stream. The T2-MI stream is itself encapsulated in a new layer of the MPTS (Multiple Program Transport Stream) type. The T2-MI stream comprises T2-MI data packets such as T2-MI timestamp synchronization packets, signaling packets including the current packet called TS-MI L1, which gives information on the structure of the T2-MI stream, and packets referred to as baseband frames containing the data of the MPEG-2 TS streams of the various tunnels. The T2-MI packets are organized in T2 frames, and each T2 frame contains a timestamp T2-MI packet, a current T2-MI L1 packet and baseband frame packets.
The T2-MI streams are synchronized by means of T2-MI timestamp packets so as to allow a synchronous broadcasting within an SFN (Single Frequency Network). These networks consist of a plurality of transmitters broadcasting the same DBV-T2 radio signal on the same frequency. This broadcasting mode is possible only if the transmitters are synchronized and the DVB-T2 radio signals transmitted are identical to within one bit, otherwise interferences will be generated in the areas covered by the transmissions of at least two transmitters.
The T2-MI streams are conventionally transmitted to at least one satellite which in return broadcasts these streams in a given geographical area. The streams broadcast by the at least one satellite are then received, modulated and retransmitted by terrestrial broadcasting stations.
The use of satellites in the transmission chain has an impact on the financial cost of the transmission. This is because the cost price of a transmission by means of a satellite depends on the bandwidth used for the transmission.
In addition, the bandwidth available in a satellite is limited and it would therefore be judicious to reduce the bandwidth necessary for the transmission of such T2-MI streams by means of a satellite.